diff --git a/src/client/linux/microdump_writer/microdump_writer.cc b/src/client/linux/microdump_writer/microdump_writer.cc
index 065ca0b7..3764eec2 100644
--- a/src/client/linux/microdump_writer/microdump_writer.cc
+++ b/src/client/linux/microdump_writer/microdump_writer.cc
@@ -483,6 +483,12 @@ class MicrodumpWriter {
 
 #if !defined(__LP64__)
   void DumpFreeSpace() {
+    const MappingInfo* stack_mapping = nullptr;
+    ThreadInfo info;
+    if (dumper_->GetThreadInfoByIndex(dumper_->GetMainThreadIndex(), &info)) {
+      stack_mapping = dumper_->FindMappingNoBias(info.stack_pointer);
+    }
+
     const google_breakpad::wasteful_vector<MappingInfo*>& mappings =
         dumper_->mappings();
     if (mappings.size() == 0) return;
@@ -515,6 +521,14 @@ class MicrodumpWriter {
         ++curr;
       }
 
+      if (mappings[curr] == stack_mapping) {
+        // Because we can't determine the top of userspace mappable
+        // memory we treat the start of the process stack as the top
+        // of the allocatable address space. Once we reach
+        // |stack_mapping| we are done scanning for free space regions.
+        break;
+      }
+
       size_t next = NextOrderedMapping(mappings, curr);
       if (next == std::numeric_limits<size_t>::max())
         break;
@@ -602,7 +616,7 @@ class MicrodumpWriter {
   // crashed process. |stack_lower_bound_| <= |stack_pointer_|
   uintptr_t stack_lower_bound_;
 
-  // The stack pointer in the crashed process.
+  // The stack pointer of the crashed thread.
   uintptr_t stack_pointer_;
 };
 }  // namespace
diff --git a/src/client/linux/minidump_writer/linux_dumper.h b/src/client/linux/minidump_writer/linux_dumper.h
index 23c78e08..3a9a2e8b 100644
--- a/src/client/linux/minidump_writer/linux_dumper.h
+++ b/src/client/linux/minidump_writer/linux_dumper.h
@@ -99,6 +99,13 @@ class LinuxDumper {
   // Returns true on success. One must have called |ThreadsSuspend| first.
   virtual bool GetThreadInfoByIndex(size_t index, ThreadInfo* info) = 0;
 
+  size_t GetMainThreadIndex() const {
+    for (size_t i = 0; i < threads_.size(); ++i) {
+      if (threads_[i] == pid_) return i;
+    }
+    return -1u;
+  }
+
   // These are only valid after a call to |Init|.
   const wasteful_vector<pid_t> &threads() { return threads_; }
   const wasteful_vector<MappingInfo*> &mappings() { return mappings_; }